European Patent Application EP 181068 entitled “Method and Device for Generic Framing Procedure Encapsulation” describes how a plurality of protocol data units (PDUs) can be cascaded into a cascaded packet which is then encapsulated in a GFP frame. A device for GFP encapsulation is also described which comprises a cascading module for cascading a plurality of PDUs to form a cascade packet and a GFP encapsulation module for encapsulating the cascade packet to obtain a GFP packet. The technique proposed by EP 181068 increases the occupation rate of the payload in a single GFP frame to improve transmission efficiency.
In order to extract a packet from a cascaded packet, however, the entire cascaded packet must be un-cascaded in EP 181068.
United States Published Patent Application US2004/0252720 describes a technique for providing multiple Fibre Channel (FC) frames in one frame-mapped GFP transport frame which follows GFP conventions except that a Distributed Delimiter marks each FC frame in the payload of the GFP transport frame.
United States published Patent Application US2005/0169275 describes a method for transmitting high-level PDUs over low-level protocols, and in particular describes how Multi-protocol label switching PDUs can be transmitted by adding a pending MPLS PDU to the payload information area (PIA) of a GFP data frame; transmitting the GFP data frame to the destination node via a transmission network, and retrieving the MPLS PDU from the PIA field of the GFP data frame at the destination node.
However, it is desirable to be able to extract a single encapsulated traffic unit from a plurality of traffic units which are carried within a carrier GFP frame without requiring all of the other traffic units to be extracted from the GFP frame.